Fig. 1. Raman spectra of the pure and the adulterated olive oils at 15 ℃

Fig. 2. Raman spectra of the pure olive oil at different temperatures

Fig. 3. Comparison of Raman spectra of the pure and the adulterated olive oils at different temperature
(a): -5 ℃; (b): -10 ℃; (c): -15 ℃; (d): -20 ℃

Fig. 4. Synchronous two-dimensional Raman correlation spectra of (a) the pure and the adulterated (b) 5%, (c) 10%, (d) 20% olive oils

Fig. 5. The dendrogram of heriarchical clustering analysis based on the synchronous two-dimensional Raman correlation spectra